I like the variants and I hope the line can continue for years to come so we can get some of these, but in an "All Star Year" I would say none of the variants are "Essential" especially when stacked up against new unique characters. It was good to mix variants in when the line was focused on being able to have a strong line up year after year, but now that the focus is on getting out the "All Stars" I think that means variants go on the back burner.
So my vote is "None". But if I was to vote for one variant I would want to see above all others included in my Classics collection I would choose NA Skeletor. But again, my real hope is that the line continue into 2016 and beyond so we can see all of these make it into our collections--they are just not essential in an "All Star Year" when there are so many characters missing and factions under-represented.